1. Field of the Invention
The present invention relates generally to methods and apparatus for analyzing stored ECG data and more particularly to such methods and apparatus which facilitate classifying the morphologies of a plurality of ECG heartbeat waveforms.
2. Description of the Related Art
In a Holter ECG monitoring system, a patient is fitted with a monitor which detects and stores continuous ECG waveforms. Sometimes several leads are connected to the patient so that two or more such waveforms are recorded. It is not unusual for such a monitor to be worn for many hours thereby generating thousands of periodic heartbeat waveforms which are stored for later review to assist in diagnosis and treatment of the patient.
Some Holter monitors include processors which automatically classify each heartbeat waveform into similar shapes or morphologies, and also identify a typical heartbeat waveform example from each morphology. After the data is collected and transferred to a system for displaying the ECG waveform, a clinician examines the example selected by automated analysis. The role of the clinician is to further group them into a minimal set of clearly-different morphologies. The clinician must examine each of the representative heartbeat waveforms provided by the Holter monitoring system and determine which are truly different and which are generally the same. Typically the clinician merges some of the morphologies as being substantially the same and, in addition, reclassifies other morphologies. For example, a morphology identified as a ventricular ectopic beat may be reclassified by the clinician as actually representing an artifact or some other beat classification.
Prior art systems provide a matrix of adjacent display screens each of which displays a heartbeat representative of a different morphology as determined by the Holter monitor. In some prior art systems, one of the representative heartbeat waveforms can be selected to be overlaid on another heartbeat waveform to facilitate comparison. Even so, it is difficult for a clinician to compare a number of ECG heartbeat waveforms, especially when they initially appear relatively similar to one another, and thereafter merge or reclassify the various morphologies.